The delivery of therapeutic to the interior lumen walls of a diseased vessel is an important, often repeated, procedure in the practice of modern medicine. Therapeutic agents may be used to treat, regenerate, or otherwise affect the interior lumen wall surface or the vessel wall itself. For example, therapeutic agent may be infused into the walls of blood vessels to inhibit or prevent restenosis of plaque within the artery. The delivery of the therapeutic can be completed by injection of the therapeutic, near the target site, through injectors. These injectors, located on the exterior of a balloon catheter inserted into the lumen, engage and embed into the interior wall of a vessel when the balloon is inflated.
Examples of catheters with therapeutic injectors are shown in U.S. Pat. Nos. 5,681,281; 5,713,863; and 6,210,392, all to Vigil et al. FIGS. 1 and 2, which are taken from U.S. Pat. No. 5,681,281, illustrate such a catheter, defined as device 10. FIG. 2, an enlarged longitudinal section view taken along line 3-3 of FIG. 1, shows injectors, 20a, 20b, 20c, and 20d, engaging and embedding into the interior vessel wall 54 upon inflating balloon 16. With the injectors embedded into the vessel wall, therapeutic is pumped from fluid source 60 (shown in FIG. 1) into the infusion chamber 26 and delivered into the vessel wall through channel 48 of each injector.
None of the above discussed patents, however, addresses the problem of the release of therapeutic directly into the bloodstream from injectors that do not engage the vessel wall. When the diseased or otherwise targeted area is irregularly shaped due to plaque deposits along the interior wall surface, or is near a side vessel or bifurcated branch vessel, the injectors may not engage the vessel wall. For example, FIG. 3 depicts catheter 10 with therapeutic injectors, 20a through 20d, in a bifurcated vessel 70. Bifurcated vessel 70 contains a side vessel branch 71 that prevents injector 20a from embedding into the interior vessel wall 72. As another example, injector 20a of FIG. 4 does not engage or embed into interior vessel wall 73 because the vessel wall is irregularly shaped. Crater 74 of the vessel wall 73 precludes the injector 20a from engaging. Cratered or otherwise irregularly shaped vessel walls are typical in arteries inflicted with arteriosclerosis.
Accordingly, when delivery of therapeutic agent is initiated, the therapeutic released from unengaged injector 20a flows directly into the bloodstream instead of into the walls of the lumen. Due to the toxic nature of some therapeutics, a therapeutic delivery catheter should minimize washing away of therapeutic agents into the blood stream. Further, more therapeutic will flow into the blood stream from an unengaged injector than will be delivered to the vessel wall from an engaged injector because the flow through an engaged injector, such as injectors 20b, 20c, and 20d of FIG. 4, encounters greater resistance, induced by the pressure of interior vessel wall 73, than the unimpeded flow through unengaged injector 20a. Thus, loss of therapeutic through unengaged injectors due to irregularly shaped or bifurcated vessels presents an impediment to the safe and effective delivery of therapeutic agents.